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Thursday, September 26, 2013

No-Carb Foods, Artificial Sweeteners & The Cravings: In The End, It's The Glucose, Not The Taste Our Brains Crave

Despite the fact that candy is per definition (literally) made of sugar, you can buy "no carb candy" at every corner. The results of this study tell you why these aren't worth the money.

I have written extensively about artificial sweeteners in the past and would thus hope that it's not necessary to recount all the information about how they interact with insulin, potential toxicity risks, their (non-existent) effects on satiety... ah, well actually I do want to talk about the last point, because it is highly relevant to understand the implications of the results of recent Yale study (Tellez. 2013).

I know, it's just a rodent study, but I guess you will feel reminded of yourselves during your diet, when I tell you about the observations Luis A Tellez, Xueying Ren, Wenfei Han, Sara Medina, Jozelia Ferreira, Catherine Yeckel and Ivan E de Araujo made an experiment that is the first to demonstrate that the lack of glucose utilization in the brain makes artificial sweetener totally unattractive to mice.

Did you ever realize that sweeteners just won't cut it, when you're hungry?

Many of you may know that: You are dieting and you are craving - food in general, but pasta, candy and all the other carbohydrate-laden foods even more so. You've been training hard and feel that your blood glucose levels are right in the no-man's land between "just high enough to keep standing" and "already so low that you have to sit down". This is the time when you will begin to feel cold. You are sweating or getting shaky (these symptoms vary from person to person), get moody or feel like you had to run even more just to abstain from doing the one thing of which you know that it would solve all your problems (temporarily): Heading over to the kiosk next door and buying the next best Snickers or Mars bar.

Yes, Adelfo Cerame is a professed, but reformed carbophobic. Learn more about how reintroducing carbs into his diet finally got him his pro-card in this and his other guest posts

The poor critters in the study Tellez et al. conducted did not have a kiosk available. What they did have, though, was glucose and artificially sweetened water. Now, the scientists conducted the same experiment in two conditions.

During condition one, the rodents were fed, satiated and happy (fed).

During condition two, however, they had been glucose deprived and were in a similar state as you may have been after the previously described workout.

What's quite telling (and by the way new) is that the glucose availability had a major impact on their sweetener preferences. When fed and happy, the mice went for the super-sweet sugar- and calorie-free artificially sweetened water.

The disgustingly sweet but glucose-free water did however lose all its appeal once the mouse brains realized that the glucose supply was becoming tight:

"Consistently, hungry mice shifted their preferences away from artificial sweeteners and in favour of glucose after experiencing glucose in a hungry state." (Tellez. 2013)

And what's more, this deliberate(?), or probably instinctive, decision to turn their back on the fake sugars and avail themselves of the "real sweet deal" of which they new it would deliver what the mice needed was immediately rewarded. Rewarded in the most physiological sense of the word: with a whopping dose of dopamine, the very hormone that entrains stimulus < > response relationships like these.

Sugar will increase dopamine, sweeteners won't

You can tell how real this "conditioning" effect was from another observation the researchers made, when they analyzed the brain activity of their lab animals and found that a big gulp from the sugar water did not just bring the blood glucose of the sugar-deprived animals back up, it

When the scientists artificially disrupted the oxidation of glucose directly at the level of the dorsal striatum, which is also known as the neostriatum or striate nucleus that is activated by stimuli associated with reward and aversive, novel, unexpected, or intense stimuli, the sweetness preferences of the mice remained the same. This observation directly supports the conclusion that we are in fact dealing with a fundamental food-reward effect here; and effect, of which you can be certain that is is also involves in "past addiction" ;-)

As the researchers themselves point out, their results demonstrate that glucose oxidation controls the intake levels of "sweet tastants" (=umbrella term for everything that stimulates the sweet taste receptors) by modulating the extracellular dopamine levels in dorsal striatum.

For you, this means that you know better than believe that you could get away with that low carb, sugar free candy bar, chewing gum or whatever else it may be that you are using to soothe your sweet tooth you are effectively cheating yourself. It works only in conjunction with your free will to avoid the carbs and usually only for so long as you allow yourself planned and controlled refeeds.

Note: When you are in full ketosis, things may be different; although the effects of ketones on dopamine levels are - afaik - not well researched, yet.

Let's finally try to draw some more general conclusions about carbohydrate intake in general - I mean beside the real sweet stuff, like candy, etc. Let's take the no-carb noodles you or hopefully not you, but your obese neighbor just bought, for example. They may taste just like the real deal. In the absences of the (expected) subsequent influx of glucose and its oxidation in the brain, they will yet never provide the hedonic response you are looking for. They are fake, a good one that may fool the first line of nutrient sensors, but a fake that's not good enough to reproduce the expected downstream effects on neurotransmitters.

Now, the good news is: No-carb noodles are probably non-addictive. The bad news, however, is: No-carb noodles are also highly, or I should say utterly unsatisfying replacement for real pasta, because the lack of carbohydrates, or rather the glucose that would get oxidized right in your brain, when you consume a bowl of real pasta is the critical physiological signal that makes pasta what it is: A highly addictive comfort food. For the average pasta junky, a "no-carb noodle" is thus never going to cut it, unless he or she is willing to cure him- or herself of her sugar addiction first.

Bottom line: Unlike "zero carb candy" or "no-carb noodles" an effective "diet aid", or let's rather say, one of the foods you should select, whenever you are trying to rid yourself of body fat (low GI starches, fruits and even vegetables (*I write "even" because the amount of carbs in some veggies borders zero)) can offer this "second line" effects in your brain; effects, none of the fake foods you buy at the supplement store, the super market and as of late even some kiosks will ever be able to produce. These real foods are the ones that will have you feel satisfied and they are the ones that should make up more than just the figurative lion's share of your diet - not the calorie, carbohydrate and nutrient free no-carb noodles and their low-carb brethren that will just have you crave the "real deal" even more.

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